In the proposed research, a detailed study will be made of the localization of mammalian sperm cell surface components in distinct surface regions. In previous work, we have isolated a collection of monoclonal antibodies to localized guinea pig sperm surface antigens. These antibodies will be used to identify the localized molecules, to analyze mechanisms that maintain sperm surface antigens in distinct regions, and to study the process of antigen localization during spermatogenesis. The role of individual surface molecules in two sperm surface functions will be studied. The acrosome reaction will be investigated to identify biochemical modifications of sperm membrane proteins that precede plasma-acrosomal membrane fusion. Fertilization studies will be undertaken to assess the capacity of individual monoclonal antibodies to block fertilization. Sperm surface components involved in fertilization may be identified.